[PATCH] migration: do not restart VM after successful snapshot-load

[Paolo Bonzini]

The HMP loadvm code is calling load_snapshot rather than
qmp_snapshot_load, in order to bypass the job infrastructure.  The code
around it is almost the same, with one difference: hmp_loadvm is
restarting the VM if load_snapshot fails, qmp_snapshot_load is doing so
if load_snapshot succeeds.

Fix the bug in QMP by moving the common code to load_snapshot.

Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 migration/savevm.c | 16 ++++++++--------
 monitor/hmp-cmds.c |  7 +------
 2 files changed, 9 insertions(+), 14 deletions(-)

diff --git a/migration/savevm.c b/migration/savevm.c
index 52e2d72e4b..a899191cbf 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2992,6 +2992,7 @@ bool load_snapshot(const char *name, const char *vmstate,
     int ret;
     AioContext *aio_context;
     MigrationIncomingState *mis = migration_incoming_get_current();
+    int saved_vm_running  = runstate_is_running();
 
     if (!bdrv_all_can_snapshot(has_devices, devices, errp)) {
         return false;
@@ -3024,6 +3025,8 @@ bool load_snapshot(const char *name, const char *vmstate,
         return false;
     }
 
+    vm_stop(RUN_STATE_RESTORE_VM);
+
     /*
      * Flush the record/replay queue. Now the VM state is going
      * to change. Therefore we don't need to preserve its consistency
@@ -3061,13 +3064,17 @@ bool load_snapshot(const char *name, const char 
*vmstate,
 
     if (ret < 0) {
         error_setg(errp, "Error %d while loading VM state", ret);
-        return false;
+        goto err_restart;
     }
 
     return true;
 
 err_drain:
     bdrv_drain_all_end();
+err_restart:
+    if (saved_vm_running) {
+        vm_start();
+    }
     return false;
 }
 
@@ -3135,17 +3142,10 @@ static void snapshot_load_job_bh(void *opaque)
 {
     Job *job = opaque;
     SnapshotJob *s = container_of(job, SnapshotJob, common);
-    int orig_vm_running;
 
     job_progress_set_remaining(&s->common, 1);
 
-    orig_vm_running = runstate_is_running();
-    vm_stop(RUN_STATE_RESTORE_VM);
-
     s->ret = load_snapshot(s->tag, s->vmstate, true, s->devices, s->errp);
-    if (s->ret && orig_vm_running) {
-        vm_start();
-    }
 
     job_progress_update(&s->common, 1);
 
diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c
index 0ad5b77477..a39436c8cb 100644
--- a/monitor/hmp-cmds.c
+++ b/monitor/hmp-cmds.c
@@ -1127,15 +1127,10 @@ void hmp_balloon(Monitor *mon, const QDict *qdict)
 
 void hmp_loadvm(Monitor *mon, const QDict *qdict)
 {
-    int saved_vm_running  = runstate_is_running();
     const char *name = qdict_get_str(qdict, "name");
     Error *err = NULL;
 
-    vm_stop(RUN_STATE_RESTORE_VM);
-
-    if (!load_snapshot(name, NULL, false, NULL, &err) && saved_vm_running) {
-        vm_start();
-    }
+    load_snapshot(name, NULL, false, NULL, &err);
     hmp_handle_error(mon, err);
 }
 
-- 
2.26.2